Physicians have used elastic ligating bands to treat lesions, including internal hemorrhoids and mucositis and for performing mechanical hemostasis.
The object of ligation is to position a ligating band over the targeted lesion or blood vessel section by stretching the band beyond its undeformed diameter drawing the tissue to be ligated within the band and then releasing the band so that it contracts, applying inward pressure on the section of tissue caught within the band. The effect of the inward pressure applied by the band is to stop all circulation through the targeted tissue, thereby causing the tissue to die. The body then sloughs off the dead tissue or the dead tissue may be aspirated into an endoscope or a similar device.
Ligating bands are typically dispensed using ligating band dispensing devices which include cylindrical support surfaces over which elastic ligating bands are stretched. The cylindrical support surfaces arc typically attached to the distal end of an endoscope which is advanced into the body to a target area. A user then applies suction through the endoscope to draw the tissue to be ligated into the cylindrical support surface and then releases a ligating band to contract around the tissue
Some ligating band dispensers use trigger lines received in slots at the distal end of a cylindrical support to roll ligating bands toward, and eventually off, the distal end of the support. A problem encountered with such devices when dispensing prior ligating bands is the bands may sometimes slide, rather than roll, along the cylindrical support. A band which slides, rather than rolls, may tend to push the trigger line ahead of it. This is disadvantageous because the trigger line may be pushed out of its slot in the distal rim of the cylindrical support, leaving a band with no trigger line attached.
Ligating bands are often made by extruding an elastic compound through a tubular die. Then tube is then cut transversely to form the bands. As a result of this process, the bands have sharp edges along both the inner and the outer diameter surfaces. Such sharp edges may cause the bands to disadvantageously slide, rather than roll, when being dispensed from devices employing a trigger line.
U.S. Pat. No. 5,356,416 to Chu et al. and U.S. Pat. No. 5,398,844 to Zaslavsky et al., both of which are incorporated herein by reference, describe other types of ligating band dispensing devices which include cylindrical support surfaces over which elastic ligating bands are stretched.
A problem inherent with the type of ligating bands typically used with the above-described devices is that the bands have a tendency to slip off the targeted tissue before the tissue is completely ligated. One reason why a ligating band may slip off targeted tissue is because tissue contained within a ligating band is effectively "pinched" by the ligating band creating an outward pressure on the band. Specifically, the bulb-shaped projection of tissue which has been drawn under suction into the lumen of a cylindrical support surface is pulled away from the surrounding tissue creating tension within the projection which draws the tissue of the projection back toward the its natural position. Thus, the tissue is urged to slip out of the ligating band as the band contracts. In additions blood and fluid within the body can make the surface of the targeted tissue slick, thereby decreasing the coefficient of friction between the ligating band and the targeted tissue. Also, if the targeted tissue is an active blood vessel the "pulsing" effect of blood moving through the vessel can cause the ligating band to slip off of the targeted tissue.
Therefore, what is needed is a ligating band. which rolls, rather than slides, as it moves toward the distal end of the dispenser housing in trigger line-type dispensers. Also what is needed is a ligating band which remains in place once dispensed onto the target tissue.